The Montreal Police arson squad has been asked to investigate the cause of a suspicious fire at a tire warehouse located at 8900 Elmslie near Dollard in LaSalle.
Firefighters were called to the warehouse at around 7pm Sunday.
They were able to bring the flames under control and declared the fire out at around 2am Monday.
But at around 5am the fire re-started.
"The roof of the warehouse collapsed as we were putting out the fire at 2am, and some debris under the roof is still smoking," Benoit Brouillard, chief of operations of the Montreal fire department,told CJAD.
Brouillard said firefighters would use a bulldozer to dig up the collapsed roof and properly extinguish the smoke underneath.
No injuries were reported and authorities said they do not consider the smoke a health risk, because the part of the warehouse that was destroyed did not contain many tires.
Firefighters told CJAD arson was suspected because the owner of the warehouse was having trouble with a former employee.